There are many documents describing accelerometers for measuring sport performances. Most of the existing accelerometers are designed for exercises lasting for a long period of time, for example to evaluate the traveled distance or the calorie expenditure during a jogging session or a cycling tour. There are also fairly similar devices for detecting elderly people falling, the time they spend sitting, standing or lying down, etc.
U.S. Pat. No. 5,788,655 (Omron) describes a device designed to be fastened onto the body and provided with an accelerometer and with an LCD. The device continuously measures the wearer's movements to determine his/her level of physical activity and other values depending on the metabolism, such as the user's daily calorie intake. This type of device is useful for measuring more objectively the level of inactivity of patients. It is however not adapted for muscle training and for measuring short efforts, and does not allow for example the maximum power of a muscle group of the athlete to be measured.
WO2005074795 (Nokia) describes a measurement terminal provided with an accelerometer and fastened onto the body of an athlete. The measurement data are assessed to supply a value representative of the intensity of the exerted effort. Again, the aim is to determine the level of activity over a long period, for example a day or a week.
US2006191335 describes a portable accelerometer designed in particular for measuring the muscular force of the legs through walking exercises.
WO03/032826 (Philips) describes a comparable system provided with a three-axis accelerometer for determining the level of physical activity of a patient. The proposed device displays values such as the daily metabolic rate, the daily energy output or the energy output induced by exercise. This device is thus useful for measuring accelerations over a period of several hours or even of several days.
None of these devices allows basic physiological muscle parameters such as strength, speed or power of a muscle group to be obtained. They are essentially suited for endurance sports, for example for jogging, and are not or only poorly adapted for the specific training of the force, power or speed of contraction of a muscle or muscle group. Without knowing the displaced mass, many devices do not make it possible to deduce the athlete's force or power. Even if this mass is known, many devices aim first and foremost to calculate the distance travelled, the average speed or the energy output, but do not allow the muscle power of a muscle group of the athlete to be determined directly, i.e. the speed at which this muscle group can displace a given mass.
U.S. Pat. No. 5,474,083 describes a system designed to monitor the load-lifting movements of a patient. The system uses electrodes for measuring the activity of the patient's muscles during the movement, as well as a load movement detector. An alarm is triggered in case of inappropriate movement. This system is useful for preventing accidents caused by incorrect load lifting or for having people practise lifting loads without injury. It is however not suited for measuring the athlete's muscular performance. Furthermore, the use of electrodes makes it inconvenient to use.
U.S. Pat. No. 6,148,280 (Virtual Technologies) describes a device provided with accelerometers and gyroscopes placed on the entire body of an athlete. The data supplied by several sensors are transmitted to a PC that allows the trajectory and other features of the movement to be analyzed. This system is complex, since it makes use of several sensors, including expensive and relatively fragile gonometers. The connection of the sensors to one another and with the external computer increases the cost of the device and makes it difficult to install. It is adapted for training precise movements, for example a golf swing, but does not allow the muscle power developed by the athlete during this movement to be determined directly.
DE446302 describes an accelerometer used in combat sports for measuring the acceleration of the strike surface. The apparatus is not portable and is suited only to combat sports such as boxing, karate, etc. An external computer must be used to assess and display the results of the measurement. It is not programmable and can be used only for a single type of exercise.
WO2007036611 (Oulun Seudun Ammattikorkeakoulu) describes a wristlet provided with an accelerometer for measuring muscular force during a load-lifting movement.
Application WO07107491 describes a portable accelerometer enabling the muscle power of an athlete or of a patient to be assessed using short tests. These tests make it possible to determine the athlete's maximum power and to select the optimum load with which an athlete must exercise to maximize the power expended during the exercise.
However, this device supplies no indication to the athlete as to the rate at which this load is to be displaced in order to achieve the desired results. Furthermore, the recommendations do not depend on qualitative objectives of the athlete nor on the performances the athlete wishes to improve. For example, this device does not distinguish between an athlete wishing to improve speed and another athlete wishing to improve power. Finally, this device is designed for short tests only, using a series of exercises imposed by the device (for example 5 jumps, 5 lifts, etc.); an error is generated if the athlete executes different movements or a different number of movements from what is prescribed by the test. This devices is thus not adapted for measuring physiological parameters during training, for example when the number of movements varies.
Other accelerometers used for measuring muscular parameters are also described in GB2422790 and in WO20005055815.